New investigation of low-lying states in Be 12 via a H 2 (B 13, He 3) reaction

We investigate the low-lying positive-parity states in Be12, which are populated by the H2(B13, He3) reaction via l=1 proton transfer for the first time using a radioactive beam B13 at 23 MeV/nucleon. Spectroscopic factors and excitation energies of these states are in reasonable agreement with the shell model predictions. Besides two bound states, we observe a resonant state at Ex=4.8±0.1MeV with an intrinsic width of 0.42±0.28 MeV, which predominately decays via one neutron to the bound states in Be11. It most likely corresponds to the En=1.24MeV state observed in the previous one-proton removal reaction. The spin-parity of 2+ is tentatively assigned to this resonance according to the analysis of its angular distributions as well as the theoretical calculations, including shell model and Gamow coupled-channel approach.